1. Field of the Invention
This invention relates to a process for doping polyaniline powder, more particularly to a process for doping polyaniline powder using a low water content dopant.
2. Description of the Related Art
Electrically conductive materials made of polyaniline powder (also known as emeraldine salt) are widely used to produce organic lighting devices, secondary batteries, anti-electrostatic coatings, conductive adhesives and coatings, electron beam photoresistive agents, sensors, electromagnetic wave shields, etc. A conventional process for producing such an electrically conductive material comprises the steps of mixing or doping undoped polyaniline with a dopant, i.e., a protonic acid selected from the group consisting of alkyl sulfuric acid, alkyl sulfonic acid and alkyl benzene sulfonic acid. A doping reaction takes place as follows: ##STR1##
However, the conventional process suffers from the following disadvantages:
(1) Since the above-described dopants are apt to absorbing water and are both oily, the dopants cannot undergo a complete doping reaction with the polyaniline powder, thereby resulting in an oily doped product. When the doped product thus obtained is employed to produce anti-electrostatic conductive coatings or is used as a photoelectric material, the oily characteristics of the doped product affect adversely the adhesion or the processing of the doped product. PA1 (2) Since the dopants cannot react completely with the polyaniline powder, the solubility of the doped product decreases, thereby resulting in difficulty to achieve a preferred situation in applying the doped product to an anti-electrostatic conductive material or a photoelectric material. PA1 (a) mixing a drying agent with a dopant selected from the group consisting of alkyl sulfuric acid, alkyl sulfonic acid, alkyl benzene sulfonic acid and dialkyl benzene sulfonic acid so as to remove water contained in the dopant; and PA1 (b) blending the dopant dried in step (a) and the polyaniline powder in the presence of an additive which is selected from the group consisting of phosphoric acid, hydrochloric acid, nitric acid and acetic acid in order to form a doped product.